Transformers play an important role in the electricity transmission and distribution process after the generation process. They are installed on substations to step down or step up the voltage values.
So, it is important to maintain their health and WTI(Winding Temperature Indicator) and OTI(Oil Temperature Indicator) are used for its monitoring.
OTI and WTI:
The device that shows us the values of oil and winding temperatures of the transformer is called OTI and WTI.
OTI represents Oil Temperature Indicator
WTI representsWinding Temperature Indicator
Why we use OTI and WTI in Transformer:
Oil is fed up in the transformer for cooling purposes and transformer winding is enclosed in a tank. Transformer winding and Oil are not for physical interaction for us, mean winding is enclosed in a tank,
So, when we have to monitor transformer winding and oil we need such a device that can tell us from the outside.
Transformer tank has:
- Core and its Winding
These are important in transformers and their continuous monitoring is required. We need to check the transformer effect on oil and winding on full load or fed/running condition. We have to perform regular basis monitoring of oil and winding.
Oil and winding temperature is directly proportional to load. So at maximum load, we will have maximum Winding temperature and transformer heating will also increase. We know winding is dipped in oil and as soon as transformer winding temperature is increasing, the oil temperature will also increase.
From the industrial point of view, we must know how to read WTI and OTI.
Now we will discuss how to read oil and winding temperature.
Here you can see a meter for Winding temperature in figure:a. this meter has 2 needles (black and red).
Black color needle tells us at present condition what is the temperature of winding.
Red color needletells us how much maximum winding temperature was rose. It mean WTI is telling us two parameters; present temperature and maximum noted temperature of winding
Similarly meter in figure: bhas 2 needles, showing oil present and maximum noted temperature like we discussed in WTI reading section.
Ranges of WTI and OTI:
We can see 150 degrees values of OTI, which means at 150-160 degrees oil will burn up. This is the maximum temperature value.
We can see 150 degrees values of WTI, which means at 150-160 degrees winding will burn up. This is maximum temperature value.
Tripping in WTI and OTI:
We can set up an alarm for tripping at a specific temperature value and at that value circuit breaker will ring alarm and after that at specific value there will be tripping in circuit breaker.
We perform wiring in circuit breaker relay. In other words, if we are not able to monitor temperature or oil values continuously, then on our set value relay will ring alarm and trip on our pre-set value.
In industries the tripping values of OTI is normally on:
Its alarm is on 80 degrees
Its tripping is on 90 degrees.
In industries the tripping values of WTI is normally on:
Its alarm is on 85 degrees
Its tripping is on 95 degrees.
Relay will take these values as an abnormal condition and will trip over these values with an alarm before tripping.
On dial of WTI and OTI is for 2 degrees. So, these meters are crucial in industry working and operation. We make sure our safety of the transformer above normal values.